Investigation of the pre-concentration possibility of scandium ores

2018
Altınsel, Yiğit
This study was aimed at investigating the possibility of obtaining a scandium (Sc) pre-concentrate from Eskişehir-Mihalıççık scandium bearing clayey ore through mineral processing methods namely attrition scrubbing, enhanced gravity separation by using falcon concentrator, magnetic separation and flotation concentration. In this context, the study began with the characterization of the run-of-mine Eskişehir-Mihalıççık scandium ore by performing mineralogical, XRD and chemical analyses. Mineralogical analysis indicated that the major Sc-bearing minerals clay minerals are montmorillonite (Al, Mg containing, smectite group clay mineral), nontronite (iron-rich, smectite group clay mineral), and also to lesser extent Sc-bearing diopside (Ca, Fe, Mg silicate mineral) and pyroxene (so-called pyroxenite, a rock-forming silicate mineral). Apart from that, calcite (CaCO3), dolomite (CaMg(CO3)2), and quartz (SiO2) were classified as the major impurity containing minerals. So in other words, obtaining a pre-concentrate enriched in scandium at the highest possible extent by the removal of gangue minerals, including calcite, quartz, and dolomite were also targeted. In the context of the characterization studies, performed elemental analysis indicated that the ore was relatively enriched in scandium content as 105 ppm by mainly concentrating in the clay minerals such as montmorillonite and nontronite. Also, the ore has relatively higher Fe content as 8.01 % and in terms of impurities, Ca, Mg, and Si grades of the ore were determined as 4.44 %, 5.16 %, and 24.45%, respectively. Based on both mineralogical and chemical analysis, Eskişehir-Mihalıççık scandium ore was determined as a Sc-bearing clayey ore. At this point, the motivation of obtaining a pre-concentrate is preparation of a feed, relatively enriched in scandium content for increasing the efficiency and effectiveness of subsequent hydrometallurgical processes. In the context of the pre-concentration studies of Eskişehir-Mihalıççık scandium ore, attrition scrubbing tests were performed initially in order to obtain a pre-concentrate enriched in scandium content by the removal of impurities such as Ca, Mg, and Si. Following the attrition scrubbing tests, operational parameters such as solid-liquid ratio, retention time and rotation speed were encountered using a statistical approach, through a full two level factorial experimental design. As the result of the optimization of the attrition scrubbing test parameters, feed that initially contains 105 ppm Sc., was enriched to 120 ppm at 85.06 % scandium recovery. Moreover, 42.93 % of Ca, 30.88 % of Mg, and 33.73 % of Si were removed in the tailings of the attrition scrubbing tests. Following the optimization of the attrition scrubbing tests, enhanced gravity separation by using falcon concentrator was performed on the previously obtained pre-concentrate in order to provide further pre-concentration and to enrich scandium content. Falcon concentrator tests were investigated in terms of the centrifugal force and fluidization water pressure. In this context, pre-concentrate of the attrition scrubbing experiments that initially contains 120 ppm Sc., was enriched to 138 ppm at 90.17 % scandium recovery. Also, 50.24 % of Ca, 26.65 % of Mg, and 20.14 % of Si were removed in the tailings of the falcon concentrator tests. By combining the results of the applied pre-concentration methods, namely attrition scrubbing and enhanced gravity separation by using falcon concentrator, a pre-concentrate that contains 138 ppm Sc was obtained at 76.70 % Sc recovery. In addition to these, 71.60% of Ca, 49.30 % of Mg, and 47.08 % of Si were removed by the present study. As an alternative method to the enhanced gravity separation by using falcon concentrator, magnetic separation tests were performed for the further concentration of the pre-concentrate obtained from the attrition scrubbing tests. However, it was seen that the magnetic separation could not achieved its goal and thereby a pre-concentrate that was enriched in scandium could not be obtained as the result of the high intensity wet magnetic separation. Apart from these, relative enrichment of previously obtained pre-concentrate in terms of scandium through flotation concentration was also attempted as an alternative method. In the flotation tests, two different flotation flowsheet was applied for the flotation of the major clayey components and the flotation of the iron-bearing minerals. As it was observed during the flotation tests, previously obtained pre-concentrate did not respond positively to the applied flotation concentration methods. So, a pre-concentrate that was enriched in scandium was could not be obtained by performing flotation method. As the result of the present study, the conditions and the parameters of the selected pre-concentration methods namely attrition scrubbing and enhanced gravity separation by using falcon concentrator that would enable the most effective means of scandium pre-concentration was identified and discussed. In addition to these, a flowsheet for the pre-concentration of the Eskişehir-Mihalıççık Scandium ore was proposed.